While following an unsuspecting team of water skiers, a great white shark enters an aquatic park through its closing gates. Meanwhile, Florida announces the opening of the park’s new underwater tunnels. Kathryn “Kay” Morgan, the park’s senior marine biologist, and her assistants notice that the resident dolphins are afraid of leaving their pen. Shelby Overman, a mechanic, dives into the water to repair and secure the gates. He is attacked by the shark and killed, leaving only his severed right arm. Later that night, two men sneak into the park and go underwater to steal coral they intend to sell, but both are killed by the shark in the process.
The next day, Kay and Michael Brody are informed of Overman’s disappearance. They go down in a submarine to look for his body, and during the search, they encounter a smaller, 10 ft (3.0 m) shark. The dolphins rescue Kay and Mike, first by warning them of the shark but getting misunderstood, then by giving them a ride back to the dolphin pen at a speed the shark can’t match, but the shark escapes back into the park. They inform Calvin Bouchard, the park manager, and it excites his hunter friend, Philip FitzRoyce, who states his intention to kill the shark on network television. Kay protests and suggests capturing and keeping the shark alive in captivity, to guarantee more publicity for the park. The shark is successfully captured by Kay, FitzRoyce, and his assistant, Jack Tate. Kay and her staff nurse the shark to health. During this time, it does not even try to attack her. Calvin, desperate to start the money rolling in immediately, orders it moved to an exhibit, despite the fact they were to wait for Kay’s blessing to do this. When she hears of it, she runs to the tank and tries to save the baby shark, but the shark dies in her arms anyway. Coldly, she permits FitzRoyce to photograph it.